Vehicle lead control

ABSTRACT

A vehicle may include rear ground traction members, front ground traction members, a rear drive system to drive the rear ground traction members, a continuously variable speed front drive system to drive the front ground traction members, a rear speed sensor to output rear speeds of the rear ground traction members, a front speed sensor to output front speeds of the front ground traction members, and a controller to select a chosen lead for a rear speed of the rear ground traction members based on evaluations of different tractive efficiencies for different leads for the rear speed. The controller may further output control signals to the continuously variable speed front drive system to drive the front ground traction members at the chosen lead.

CROSS-REFERENCE TO RELATED PATENT APPLICATIONS

The present non-provisional patent application claims priority under 35USC 119 from U.S. provisional Patent Application Ser. No. 63/307,016filed on Feb. 4, 2022, by Omohundro et al. and entitled SLIP CONTROL,the full disclosure of which is hereby incorporated by reference.

BACKGROUND

A vehicle “lead” refers to the rotational speed of the front wheels orother front traction members of the vehicle, relative to the rotationalspeed at which the rear wheels or other rear traction members of thevehicle are driven. In many vehicles, the front wheels (tires) have asmaller diameter than the rear wheels. As a result, the front wheelsmust rotate faster to cover the same distance as rear wheels. Manyvehicles utilize a fixed mechanical ratio between the rear wheels andthe front wheels to establish a fixed lead based upon wheel size.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram having an example lead control system.

FIG. 2 is a flow diagram of an example method that may be carried out bythe example vehicle of FIG. 1 .

FIG. 3 is a diagram schematically illustrating an example database ofleads and corresponding tractive efficiencies for different rear speeds,wherein the database may be used by the vehicle of FIG. 1 .

FIG. 4 is a diagram schematically illustrating an example table ofoptimum leads (those having the greatest tractive efficiencies) atdifferent rear speeds, wherein the database may be used by the vehicleof FIG. 1 .

FIG. 5 is a flow diagram of an example method that may be carried out bythe vehicle of FIG. 1 .

FIG. 6 is a flow diagram of an example method that may be carried out bythe vehicle of FIG. 1 .

FIG. 7 is a diagram schematically illustrating an example database ofleads and corresponding tractive efficiencies for different rear speedson different terrains.

FIG. 8 is a diagram schematically illustrating an example database ofleads and corresponding tractive efficiencies for different rear speedsin different geographic regions.

FIG. 9 is a diagram schematically illustrating an example database ofleads and corresponding tractive efficiencies for different rear speedswith different drafts or implement types and/or states.

FIG. 10 is a diagram schematically illustrating an example database ofleads and corresponding tractive efficiencies for different rear speedswith different terrains and different drafts or implement types and/orstates.

FIG. 11 is a diagram schematically illustrating an example database ofleads and corresponding tractive efficiencies for different rear speedsin different geographic regions and with different drafts or implementtypes and/or states.

FIG. 12 is a diagram schematically illustrating an example set of leadmaps for different rear speeds, each of the maps mapping differentoptimum leads for different regions.

FIG. 13 is a diagram schematically illustrating an example set of leadmaps for different rear speeds and different drafts or implement typesand/or states, each of the maps mapping different optimum leads fordifferent regions.

FIG. 14 is a top illustrating an example vehicle comprising an examplelead control system, with portions being schematically illustrated.

FIG. 15 is an enlarged fragmentary side view of an example clevis hitch,hitch pin and strain sensor of the vehicle of FIG. 14 .

FIG. 16 is a bottom view of the example vehicle of FIG. 14 , withportions being schematically illustrated.

FIG. 17 is a fragmentary sectional view illustrating portions of anexample propulsion system of the example vehicle of FIG. 14 .

FIG. 18 is a diagram schematically illustrating an example database ofleads and corresponding tractions for different rear speeds in differentgeographic regions and with different drafts or implement types and/orstates.

Throughout the drawings, identical reference numbers designate similar,but not necessarily identical, elements. The figures are not necessarilyto scale, and the size of some parts may be exaggerated to more clearlyillustrate the example shown. Moreover, the drawings provide examplesand/or implementations consistent with the description; however, thedescription is not limited to the examples and/or implementationsprovided in the drawings.

DETAILED DESCRIPTION OF EXAMPLES

Disclosed are example vehicles and methods for controlling and adjustingthe lead of a vehicle to enhance tractive efficiencies of a vehicle.Disclosed is an example vehicle having a controller that determines andselects a chosen lead for a given rear speed of the rear ground tractionmembers based upon evaluations of different tractive efficiencies fordifferent leads for the rear speed. In some implementations, thecontroller automatically outputs control signals to cause the frontground traction members to be driven at the chosen lead. In someimplementations, the controller outputs a recommendation for the chosenlead to an operator and awaits the operator input or authorizationbefore operating the vehicle with the chosen lead.

For purposes of this disclosure, “tractive efficiency” refers to theefficiency at which the vehicle converts power into the actual groundspeed of the vehicle with a corresponding pulling force. The power beingconverted may be determined based upon the torque applied to the groundengaging members of the vehicle and the speed at which the groundengaging traction members are driven (referred to as wheel speed).

The ground speed of the vehicle refers to the actual speed at which thevehicle is traveling. The ground speed may be determined using signalsfrom sensors such as GPS based sensors or radar/Doppler based sensors.

The pulling force may be referred to as the draft of the vehicle. Thepulling force may depend upon the weight of the implement being pulledby the vehicle and any interactions of the implement with the terrain.The pulling force or draft of the vehicle may be determined based uponsignals from a draft sensor.

The torque refers to the force or amount of torque utilized to drive thetraction members or wheels. In some implementations, torque may bedetermined using a strain sensor. In some implementations where theground traction members are electrically driven with a motor (such aswith the motor directly driving the wheels or the motor driving ahydraulic pump which drives a hydraulic motor to drive the wheels),torque may be determined based upon electrical current drawn by themotor. In those implementations where the ground traction members aredriven by a hydraulic motor, torque may be determined based upon signalsfrom sensors that measure hydraulic pressure. The wheel speed refers tothe rotational speed at which the rear ground traction members are beingdriven (for example, revolutions per minute (RPM)). In someimplementations, tractive efficiency may be determined based upon thefollowing formula: (Ground speed*draft)/(torque*wheel speed).

In some implementations, tractive efficiency may be determined basedupon a measurement of fuel or battery power consumption for a particularlead when other external factors are maintained constant. The powerbeing converted is a measurement related to the fuel or battery powerconsumption. In such an implementation, tractive efficiency may bedetermined by evaluating how much fuel or battery power was consumed bythe vehicle to pull an implement, providing a given load or draft, at aparticular ground speed. This evaluation may be done for each evaluatedwheel speed and each of the leads being evaluated for each wheel speeds.The results may be recorded to form a database of leads and tractiveefficiencies for different wheel speeds. As described hereafter, theresults may be further conditioned or based on variations in theimplement being towed (variations in the draft) and/or variations withrespect to the underlying terrain.

In some implementations, the rear speed for which a particular lead forthe front ground traction members is chosen is based upon a ground speedinput from an operator. The operator, using a ground speed input, suchas a pedal, lever, touchscreen, switch, slide bar, mouse and screen orother input device may enter a chosen ground speed, the speed at whichthe vehicle itself is to travel or traverse a terrain. Based upon thisentered or input ground speed, the controller may determine the rearspeed for the rear ground traction members. The controller may thenevaluate the tractive efficiencies for multiple different leads of thefront ground traction members for the rear speed to determine which ofthe different leads should be chosen. For example, at a particular rearspeed RS1, the vehicle may have: (1) a first tractive efficiency TE1when the front speed has a first lead L1 relative to the rear speed RS1;(2) a second tractive efficiency TE2, greater than TE1, when the frontspeed has a second lead L2 relative to the rear speed RS1; (3) atractive efficiency TE3, less than TE1, when front speed has a thirdlead L3 relative to the rear speed RS1. In response to the operatorselecting a ground speed having the corresponding RS1, the controllermay select the particular lead having the greatest tractive efficiency,in this example, lead L2 for the speed RS1.

In some implementations, the controller may choose the lead having thegreatest tractive efficiency. In some implementations, the controllermay choose the lead based upon additional factors, such as energyconsumption. In some implementations, evaluations or comparisons of thedifferent tractive efficiency for different leads for differentparticular rear speeds may be pre-performed for specific vehicleconfigurations and ground conditions, wherein the controller simplyidentifies the individual pre-chosen lead associated with the given rearspeed.

In some implementations, the chosen lead and the rear speed are bothselected by the controller based upon evaluations of different tractiveefficiencies for different leads. In other words, the controller maychoose a lead having the greatest tractive efficiency across multipleavailable rear speeds. Different rear speeds may have differentassociated optimal tractive efficiency leads. The tractive efficienciesamongst the different optimal tractive efficiency leads may vary. Thecontroller may compare the different tractive efficiencies amongst thedifferent optimal tractive efficiency leads to identify which optimaltractive efficiency lead (and which associated rear speed) has thegreatest tractive efficiency.

For example, at a rear speed RS1, the vehicle may have the greatesttractive efficiency TE1 with a particular lead L1. At a speed RS2, thevehicle may have the greatest tractive efficiency TE2 at a particularlead L2. The tractive efficiency TE2 may be greater than the tractiveefficiency TE1. Based upon this comparison, the controller mayautomatically select RS2 and lead L2 for the vehicle operation toachieve the greatest tractive efficiency TE2.

In some implementations, the vehicle may comprise a database comprisingthe evaluations of different tractive efficiencies for different leadsfor each of multiple different rear speeds. In some implementations, thecontroller is configured to select the chosen lead additionally basedupon the geographic location of the vehicle. In some implementations,the vehicle may comprise a lead map that identifies differentrecommended leads for a given rear speed at different geographiclocations. In such an implementation, the controller is configured toconsult the lead map based upon the current geographic location of thevehicle.

In some implementations, the controller is configured to select thechosen lead additionally based upon a current condition and such or typeof terrain underlying the vehicle. The condition (moisture content) ortype of the underlying terrain may have an impact upon the tractiveefficiencies of different leads. For a first soil type or condition, anoptimal tractive efficiency may be achieved with a first lead when therear traction members or wheels of the vehicle or at a particular rearspeed. For a second soil type or condition, different than the firstsoil type or condition, the optimal tractive efficiency may be achievedwith a second lead, different than the first lead, when the reartraction members or wheels of the vehicle are at the particular rearspeed. In some implementations, the vehicle may include a sensor tosense the current condition and such or type of terrain underlying thevehicle. In some implementations, the vehicle may include and thecontroller may consult a terrain map identifying different conditionsand/or types of terrain at different geographic locations, wherein thecontroller is configured to consult the terrain map based upon thecurrent geographic location of the vehicle to determine the currentand/or type of the underlying terrain.

In some implementations, the chosen lead may be additionally based upona current draft of the vehicle. The draft of the vehicle refers to thetowing or pulling force being exerted by the vehicle to pull animplement or attachment. The current draft of the vehicle may have animpact upon the tractive efficiencies of different leads. For a firstdraft, an optimal tractive efficiency may be achieved with a first leadwhen the rear traction members or wheels of the vehicle or at aparticular rear speed. For a second draft, different than the firstdraft, the optimal tractive efficiency may be achieved with a secondlead, different than the first lead, when the rear traction members orwheels of the vehicle are at the particular rear speed. The controllermay select the chosen lead based upon which particular lead for thecurrent draft has the optimal tractive efficiency.

In some implementations, the draft of the vehicle may be sensed. In someimplementations, the draft of the vehicle may be determined based uponthe current implement being pulled or towed by the vehicle or thecurrent state of the implement being pulled or towed. The state of thevehicle being pulled or towed may refer to whether the implement israised or lowered, is engaging the ground or carrying out a particularoperation. In some implementations, the vehicle may include a sensor todetect an identity, or an operational state of the implement being towedand then identify a corresponding draft associated with the identifiedidentity or operational state of the implement. In some implementations,an operator may input a value for the draft or an identity of theimplement and/or its state, wherein the chosen lead is based upon theidentification of the implement or its state.

In some implementations, the controller may select the chosen lead basedupon which particular lead for the current draft and the current soiltype and/or condition has the optimal tractive efficiency. In someimplementations, the vehicle may include or have access to a database ortable which, for each of a plurality of different rear speeds, tirepressures, different drafts (or different implements), and differentsoil type and/or conditions, provides a lead value identified as havingthe optimal tractive efficiency. In some implementations, the databasemay be more detailed, including multiple lead values and associatedtractive efficiencies for each individual rear speed with a given draftand with a given soil condition and/or type.

In some implementations, the controller may be configured to determineand record, in real-time, different tractive efficiencies for differentleads for each of multiple different rear speeds of the vehicle. In someimplementations, the vehicle may comprise a ground speed sensor tooutput signals indicating a ground speed of the vehicle and a torquesensor to output signals indicating torque applied to the rear groundtraction members and the front ground traction members. In someimplementations, the torque value used for determining differenttractive efficiencies may be determined based upon electrical currentsdrawn by an electric motor that directly or indirectly drives the groundtraction members. In some implementations, the draft value used fordetermining the different tractive efficiencies may be input by anoperator, directly sensed, such as with a draft sensor, or determinedbased upon an identification of an implement or attachment being pulledby the vehicle (and/or its state), wherein the identification of theimplement or attachment (and/or its state) is either input by anoperator or sensed.

In some implementations, the controller may adjust the rear speed of thevehicle, wherein for each individual rear speed of the vehicle, thecontroller may further adjust the speed of the front ground tractionmembers or wheels to provide different leads. For each of the leads ateach individual rear speed, the controller may utilize ground speed,draft, torque and wheel speed data (discussed above) to determine theresulting tractive efficiency. In such an implementation, the controllermay generate a table or database identifying different tractiveefficiencies for different leads for each of the different rear speeds.

In some implementations, the controller may record the differenttractive efficiencies for the different leads for each of the differentrear speeds with different draft values, such as when the vehicle ispulling different implements, producing a database that further takesinto account the particular draft being pulled by the vehicle. In someimplementations, the controller may record the different tractiveefficiencies for the different leads for each of the different rearspeeds when the vehicle traveling at different geographic locations oris traveling across different terrains having different soil conditionsand/or types, producing a database that further takes into account theparticular terrain or condition of the underlying terrain or soil. Suchdatabases may be subsequently utilized by other vehicles of the sametype or may be used as a basis for the selection of chosen leads theother different types of vehicles.

Disclosed is an example vehicle having controller that determines ageographic location of the vehicle and adjusts the lead of the vehiclebased on the geographical location of the vehicle. In someimplementations, the geographical location is utilized to consult a mapto determine a soil type and/or condition. The lead of the vehicle isbased on the soil type and/or condition.

In some implementations, an example vehicle directly senses soil typeand/or condition. Based on the soil type and/or condition, a controlleradjusts the lead of the vehicle.

Disclosed is an example vehicle that comprises a propulsion system. Thepropulsion system comprises an electric motor and a transaxle operablycoupled to the electric motor. The transaxle has a first portion coupledto rear ground traction members to rotatably drive the rear groundtraction members. The propulsion system further includes a hydraulicpump driven by the electric motor, a hydraulic motor driven by thehydraulic pump and a planetary gear assembly. The planetary gearassembly comprises a sun gear coupled to and driven by the hydraulicmotor, a ring gear coupled to the transaxle for being driven by theelectric motor; and a planet carrier carrying planet gears intermeshingbetween the ring gear and the sun gear. The planet carrier has an outputshaft operably coupled to the front ground traction members to drive thefront ground traction members.

In some implementations, the vehicle comprises a controller that isconfigured to modulate the hydraulic motor to control the lead of thevehicle. In some implementations, the controller is configured toperform comparisons of different ground speeds of the vehicle atdifferent rotational speeds of the front ground traction members and tomodulate the hydraulic motor to control the vehicle lead based upon thecomparisons. In some implementations, the vehicle comprises a soilsensing system that senses a soil type and such or condition, whereinthe controller is configured to modulate the hydraulic motor to controlthe vehicle lead based upon a combination of the comparisons and thesensed soil type and such or condition.

In other implementations, such implementations may alternatively oradditionally provide an operator with the ability to the vehiclemeasures traction and/or automatically selects and executes a vehiclelead based upon such tractions or traction levels. In other words,traction, rather than traction efficiency, is the target variable. Leadwill be selected to optimize the traction, rather than the tractionefficiency, for the vehicle.

Maximum traction can be determined, similarly, but based on the maximumreadings of the draft sensor until the draft stops increasing and levelsoff or goes down. Maximum traction, or coefficient of traction, can beuseful in momentary situations for the vehicle to deal with patches ofhard soil. In such example implementations, a lead control system may beoperable in a operator selectable mode in which the system consultsdatabases or tables, wherein the targeted variable is traction ratherthan traction efficiency. The system may automatically output controlsignals causing the vehicle to provide a particular lead at a particularrear speed to achieve an optimum or maximum traction for the vehicle.The database or tables may be based upon a single variable, such as rearspeed (combined with default or standard variables such as draft,implement type or state, geographic region, tire pressure or terrain) ormay be based upon combinations of multiple variables comprising one ormore of rear speed, draft, implement type or state, geographic region,tire pressure and terrain.

For purposes of this application, the term “processing unit” shall meana presently developed or future developed computing hardware thatexecutes sequences of instructions contained in a non-transitory memory.Execution of the sequences of instructions causes the processing unit toperform steps such as generating control signals. The instructions maybe loaded in a random-access memory (RAM) for execution by theprocessing unit from a read only memory (ROM), a mass storage device, orsome other persistent storage. In other embodiments, hard wiredcircuitry may be used in place of or in combination with softwareinstructions to implement the functions described. For example, acontroller may be embodied as part of one or more application-specificintegrated circuits (ASICs). Unless otherwise specifically noted, thecontroller is not limited to any specific combination of hardwarecircuitry and software, nor to any particular source for theinstructions executed by the processing unit.

For purposes of this disclosure, the term “coupled” shall mean thejoining of two members directly or indirectly to one another. Suchjoining may be stationary in nature or movable in nature. Such joiningmay be achieved with the two members, or the two members and anyadditional intermediate members being integrally formed as a singleunitary body with one another or with the two members or the two membersand any additional intermediate member being attached to one another.Such joining may be permanent in nature or alternatively may beremovable or releasable in nature. The term “operably coupled” shallmean that two members are directly or indirectly joined such that motionmay be transmitted from one member to the other member directly or viaintermediate members.

For purposes of this disclosure, the phrase “configured to” denotes anactual state of configuration that fundamentally ties the statedfunction/use to the physical characteristics of the feature proceedingthe phrase “configured to”.

For purposes of this disclosure, unless explicitly recited to thecontrary, the determination of something “based on” or “based upon”certain information or factors means that the determination is made as aresult of or using at least such information or factors; it does notnecessarily mean that the determination is made solely using suchinformation or factors. For purposes of this disclosure, unlessexplicitly recited to the contrary, an action or response “based on” or“based upon” certain information or factors means that the action is inresponse to or as a result of such information or factors; it does notnecessarily mean that the action results solely in response to suchinformation or factors.

FIG. 1 is a diagram illustrating portions of an example vehicle 10comprising an example vehicle lead control system 20. Vehicle leadcontrol system 20 facilitates the adjustment of the lead of vehicle 10to enhance tractive efficiencies of vehicle 10. Vehicle 10 comprises aframe 22 supporting rear ground traction members 24, front groundtraction members 26, and a propulsion system 28 comprising a rear drivesystem 30 and a continuously variable speed front drive system 32.

Frame 22 forms a part of a chassis of vehicle 10 and supports theremaining components of vehicle 10. Rear ground traction members 24 arelocated near a rear of frame 22 and engage the underlying terrain orground during driving of vehicle 10. In some implementations, rearground traction members 24 comprise wheels. In other implementations,rear ground traction members 24 may comprise track members (drivenground engaging belts).

Front ground traction members 26 are located near the front of frame 22.In some implementations, front ground traction members 26 are configuredto be steered to control the direction in which vehicle 10 travels.Front ground traction members 26 engage the underlying terrain orground. In some implementations, front ground traction members 26comprise wheels. In other implementations, front ground traction members26 may comprise track members (driven ground engaging belts).

Propulsion system 28 comprises the mechanism of vehicle 10 configured topropel or drive vehicle 10 in a forward direction or reverse direction,depending upon the state of an associated transmission. Propulsionsystem 28 may rely upon stored electrical energy, generated electricalenergy and/or mechanical energy derived from an internal combustionengine. Propulsion system 28 may comprise at least one battery and atleast one electric motor for propelling vehicle 10. Propulsion system 28may comprise at least one hydraulic pump and at least one hydraulicmotor for propelling vehicle 10. Propulsion system 28 may comprise aninternal combustion engine.

Rear drive system 30 comprises that portion of the propulsion system 28configured to rotatably drive rear ground traction members 24. Thecontinuously variable speed front drive system 32 comprises that portionof propulsion system 28 configured to rotatably drive the front groundtraction members 26. Front drive system 32 is configured todisproportionally increase or decrease the rotational speed of frontground traction members 26 relative to the rotational speed at whichrear ground traction members 24 are driven by rear drive system 30.Front drive system 32 is continuously variable in that the rotationalspeed at which the front ground traction members 26 are rotatably drivenmay be selectively adjusted to any one of a continuum of differentrotational speeds within a range of speeds. Front drive system 32facilitates the adjustment of vehicle lead, the adjustment of therotational speed of the front wheels of the vehicle relative to therotational speed at which the rear wheels of the vehicle are driven.

Vehicle lead control system 20 comprises rear speed sensor 50, frontspeed sensor 54, and controller 60. Rear speed sensor 50 comprise asensor configured to output signals indicating a current rotationalspeed at which rear drive system 30 is rotatably driving rear groundtraction members 24. Such signals may directly indicate the sensedrotational velocity of rear ground traction members 24 or may beindirectly indicate the sensed rotational velocity of the rear groundtraction members 24, wherein the rotational velocity may be derived fromsuch signals by controller 60. In one example implementation, rear speedsensor 50 may comprise what is commercially available as a “wheel speedsensor” or “vehicle speed sensor”. Such a wheel speed sensors maycomprise a toothed ring and pickup sized to read the speed of vehiclewheel rotation. Such sensors may utilize optics, magnetics or othermechanisms.

Front speed sensor 54 is similar to rear speed sensor 50 except thatfront speed sensor 54 comprises a sensor configured to output signalsindicating a current rotational speed at which the continuously variablespeed front drive system 32 is rotatably driving the front groundtraction members 26. Such signals may directly indicate the sensedrotational velocity of front ground traction members 26 or may beindirectly indicate the sensed rotational velocity of the front groundtraction members 26, wherein the rotational velocity may be derived fromsuch signals by controller 60. In one example implementation, frontspeed sensor 54 may comprise what is commercially available as a “wheelspeed sensor” or “vehicle speed sensor”. Such a wheel speed sensors maycomprise a toothed ring and pickup sized to read the speed of vehiclewheel rotation. Such sensors may utilize optics, magnetics or othermechanisms.

Controller 60 receives signals from sensors 50 and 54. Controller 60comprises memory 62 and processor 64. Memory 62 comprises anon-transitory computer-readable medium containing instructions fordirecting processor 64. Processor 64 comprises a processing unitconfigured to follow such instruction contained in memory 62 and carryout the example method 100 outlined in FIG. 2 .

As indicated by block 112 in FIG. 2 , instructions in memory 62 directprocessor 64 to determine and select a chosen lead for a given rearspeed of the rear ground traction members 24 based upon evaluations ofdifferent tractive efficiencies for different leads for the rear speed.FIG. 3 illustrates an example database 150 containing previouslydetermined tractive efficiency determinations for different candidateleads for the different rear speeds, the speeds at which the rear groundtraction members 24 are being driven. As shown by FIG. 3 , for the rearspeeds RS1, RS2 . . . RS_(N), the database comprises tables 151-1, 152-2. . . 151-N, respectively, identifying the previously determinedtractive efficiencies TEs for each candidate lead L. For example, whenthe rear ground traction members 24 are driven at a rear speed RS2,driving the front ground traction members 26 with the lead L1 in table151-2 will result in an estimated tractive efficiency of TE1 and table151-2. For each individual RS, there may exist a particular lead Lassociated with the greatest tractive efficiency TE. In the circumstancewhere the rear ground traction members or wheels 24 of vehicle 10 arebeing driven at the rear speed RS2 controller 60 may select theparticular lead in table 151-2 having the greatest tractive efficiencyTE as the chosen lead. In circumstances where the rear ground tractionmembers of wheel 24 of vehicle 10 are being driven at the rear speedRS1, controller 60 may select the particular lead having the greatesttractive efficiency TE in table 151-1 as chosen lead.

As shown by FIG. 4 , in some implementations, database 150 may besimplified so as to comprise a single table 154 providing the particularlead L having the optimum or maximum tractive efficiency for each rearspeeds RS. In other words, the comparison of the different tractiveefficiencies for a particular rear speed RS has been previously made andincorporated into the refined table 154. In such an implementation,controller 60 may consult table 154 and select the chosen lead byidentifying the particular lead L in table 154 that corresponds to thecurrent rear speed at which the rear ground traction members 24 arebeing driven.

As indicated by block 116, instructions in memory 62 direct processor 64to output control signals to the continuously variable speed front drivesystem 32 to drive the front ground traction members 26 at the chosenlead, at the selected rotational speed RPM relative to the rotationalspeed RPM at which the rear ground traction members 24 are being driven.In some implementations, the controller 60 automatically outputs thecontrol signals to cause the front ground traction members 26 to bedriven at the chosen lead. In some implementations, the controller 60outputs a recommendation for the chosen lead to an operator and awaitsthe operator interface or authorization before outputting the controlsignals to operate the vehicle with the chosen lead.

In some implementations, the rear speed (recited block 112) for which aparticular lead for the front ground traction members is chosen is basedupon a ground speed input from an operator. In such an implementation,controller 60 may carry out method 200 set forth in FIG. 5 . Asindicated by block 206, controller 60 receives a ground speed input froman operator interface. The operator, using a ground speed input, such asa pedal, lever, touchscreen, switch, slide bar, mouse and screen orother input device may enter a chosen ground speed, the speed at whichthe vehicle itself is to travel or traverse a terrain.

As indicated by block 208, based upon this entered or input groundspeed, the controller 60 may determine the rear speed for the rearground traction members 24.

As indicated by block 212, the controller may then select a chosen leadfor the rear speed determined in block 208 based upon an evaluation ofdifferent tractive efficiencies for different leads for the rear speed.As discussed above with respect to block 112, controller 60 may consultthat portion of database 150 or the table 154 pertaining to the rearspeed identified in block 208. Consulting that portion of database 150are table 154, controller 60 may identify the particular lead L havingthe associated greatest tractive efficiency TE for the rear speedidentified in block 208.

As indicated by block 216, instructions in memory 62 direct processor 64to output control signals to the continuously variable speed front drivesystem 32 to drive the front ground traction members 26 at the chosenlead, at the selected rotational speed relative to the rotational speedRPM at which the rear ground traction members 24 are being driven. Insome implementations, the controller 60 automatically outputs thecontrol signals to cause the front ground traction members 26 to bedriven at the chosen lead. In some implementations, the controller 60outputs a recommendation for the chosen lead to an operator and awaitsthe operator interface or authorization before outputting the controlsignals to operate the vehicle with the chosen lead.

In some implementations or when vehicle 10 is operating under a selectedmode, the chosen lead and the rear speed are both selected by thecontroller 60 based upon evaluations of different tractive efficienciesfor different leads. FIG. 6 is a flow diagram of an example method 300that may be carried out by controller 60 pursuant to an operatorselected mode. When carrying out method 300, controller 60 may choose alead having the greatest tractive efficiency across multiple availablerear speeds.

As indicated by block 302 in FIG. 6 , controller 60 may select a rearspeed based upon different tractive efficiencies for different leads foreach of multiple different rear speeds. As indicated by block 304,controller 60 may further select a chosen lead for the rear speed ofrear ground traction members based upon an evaluation of differenttractive efficiencies for different leads for the rear speed. Pursuantto blocks 302 and 304, controller 60 may compare the different tractiveefficiencies in all of the tables 151 to identify which optimal tractiveefficiency lead (and which associated rear speed) has the greatesttractive efficiency. The chosen lead will be the lead corresponding tothe greatest tractive efficiency. The selected or chosen rear speed willbe the rear speed corresponding to the greatest tractive efficiency. Forexample, if tractive efficiency TE2 in table 151-2 is identified ashaving the greatest tractive efficiency amongst all of the tractiveefficiencies in all of tables 151, the chosen lead will be the value ofL2 in table 151-2 and the chosen rear speed will be RS2.

As indicated by block 306, once the chosen rear speed and the chosenlead have been selected, controller 60 may output control signals to therear drive system 28 to drive the rear ground traction members 24 at thechosen rear speed. As indicated by block 308, controller 60 may outputcontrol signals to the continuously variable speed front drive system 32to drive the front ground traction members 26 at the chosen lead. Asdiscussed above, in some implementations, the switching of vehicle 10 tothe chosen rear speed for traction members 24 and the chosen lead fortraction members 26 may be automatic. In some implementations,controller 60 may alternatively output a recommended rear speed to theoperator, wherein controller 60 outputs such control signals uponreceiving further input or commands from the operator authorizing theswitch of vehicle 10 to the chosen rear speed and the chosen lead.

In some implementations, controller 60 may select the chosen lead basedupon additional factors that may impact tractive efficiency. In somecircumstances, the type of underlying terrain, such as the type of soil,or the condition of the underlying terrain, such as moisture content ofthe soil, may impact the tractive efficiencies associated with differentvehicle leads at different rear speeds. In some implementations,controller 60 may select the chosen lead additionally based upon thecurrent type or conditions of the terrain underlying the vehicle 10.

FIG. 7 illustrates an example database 450 that may be consulted bycontroller 60 when selecting a chosen lead for vehicle 10 at either arear speed based upon an operator interface (such as described abovewith respect to method 200) or a chosen rear speed (such as describedabove with respect to method 300). Database 450 comprises an individualdataset (similar to database 150) for each of multiple different terrainconditions and/or types. In the example illustrated, database 450comprises data sets 451-1, 451-2 . . . 451-N (collectively referred toas data sets 451) for the different terrain types/conditions T1, T2 . .. TN, respectively. Each of data sets 451 is similar to database 150described above except that its values have been determined when vehicle10 or a vehicle similar to vehicle 10 has been traveling across anunderlying terrain having the particular terrain type or condition.

In such an implementation, controller 60 may receive signals from aterrain sensor, such as a camera. Controller 60 may identify ordetermine the type or condition of the soil based upon signals from theterrain sensor. Controller 60 may use the determined type or conditionof terrain to determine which of the data sets 451 should be consultedfor further selecting a chosen lead for vehicle 10.

Alternatively, controller 60 may determine the geographical location ofthe vehicle 10 (based upon signals from a location sensor, such as aglobal positioning system (GPS) sensor) and may use the determinedgeographical location to consult a terrain map which provides orindicates the current conditions or type of the terrain for thegeographical location at which the vehicle currently resides. In someimplementations, the operator may provide controller 60 with the type orcondition of the soil or terrain to facilitate the determination ofwhich of data sets 451 should be consulted for selecting the chosenlead. In some implementations, the operator may directly indicate tocontroller 60 (via an operator interface) which of the data sets 451should be used for selecting the chosen lead.

In some implementations, controller 60 may consult a database such asdatabase 550 illustrated in FIG. 8 when selecting a chosen lead.Database 550 is similar to database 450 except that database 550comprises an individual data set (similar to database 150) for each ofmultiple different geographical locations GR. In the exampleillustrated, database 550 comprises data sets 551-1, 551-2 . . . 551-N(collectively referred to as data sets 551) for the differentgeographical regions GR1, GR2 . . . GRN, respectively. Each of data sets551 is similar to database 150 described above except that its valueshave been determined when vehicle 10 or vehicle similar to vehicle 10has been traveling within a particular geographic region.

In some implementations, the values of database 550 may be determinedbased upon different terrain type/conditions (soil type/conditions) indifferent regions. For example, the terrain types or conditions may beobtained from prior maps or surveys. Based upon the determined terraintypes or conditions, the expected tractive efficiencies for thedifferent geographical regions having the different terrain types orconditions may be estimated.

In such implementations, controller 60 may determine the geographicallocation of the vehicle 10 (based upon signals from a location sensor,such as a global positioning system (GPS) sensor) and may use thedetermined geographical location to determine which of the data sets 551should be consulted for selecting a chosen lead. In someimplementations, the operator may provide controller 60 with theparticular geographic region in which vehicle 10 is traveling oroperating to facilitate the determination of which of data sets 551should be consulted for selecting the chosen lead. In someimplementations, the operator may directly indicate to controller 60(via an operator interface) which of the data sets 551 should be usedfor selecting the chosen lead.

In each of the above databases or tables, the tractive efficiencies arebased upon a default or nominal draft value, the pulling force providedby the vehicle 10 when at a particular ground speed correspond to therear speed. The default or nominal draft value may be based upon aparticular implement expected to be pulled or towed by vehicle 10. Insome implementations, the tractive efficiency may be based upon anaverage draft value expected to be provided by or experienced by vehicle10. In some implementations, vehicle 10 may be configured to pull or towdifferent types of implements resulting in different drafts. In suchimplementations, controller 60 may select the chosen lead additionallybased upon the current draft of the vehicle 10.

FIG. 9 illustrates an example database 650 that may be consulted bycontroller 60 when selecting a chosen lead for vehicle 10 at either arear speed based upon an operator interface (such as described abovewith respect to method 200) or a chosen rear speed (such as describedabove with respect to method 300). Database 650 comprise an individualdata set (similar to database 150) for each of multiple different draftvalues or multiple different implement types. In the exampleillustrated, database 650 comprises data sets 651-1, 651-2 . . . 651-N(collectively referred to as data sets 651) for the different drafts orimplement types D/I 1, D/I2 . . . D/I-N, respectively. Each of data sets651 is similar to database 150 described above except that its valueshave been determined when vehicle 10 or vehicle similar to vehicle 10has pulled or towed particular type of implement or provided aparticular draft (pulling force) or range of draft values.

In such implementations, controller 60 may determine the current draftof the vehicle 10 (based upon signals from a draft sensor, such as ahitch pin connecting the implement drawbar to the vehicle and having astrain sensor or based upon signals from various strain sensors attachedto the links of the three-point hitch). In some implementations, thevehicle may be equipped with an implement sensor to detect or sense theimplement and its current operational state. For example, the vehiclemay be equipped with a camera and a neural network that utilizes opticalrecognition to identify the particular implement. Once a particularimplement has been identified, the draft associated with the implementand its operation may be determined to determine which of the data sets651 should be consulted or, where the data sets 651 are based uponimplement type, the type of implement may be used to directly determinewhich data set 651 should be consulted for selecting the chosen lead. Insome implementations, the operator may provide controller 60 with theimplement type or draft value to facilitate the determination of whichof data sets 551 should be consulted for selecting the chosen lead. Insome implementations, the operator may directly indicate to controller60 (via an operator interface) which of the data sets 651 should be usedfor selecting the chosen lead.

In some implementations, controller 60 may select the chosen lead basedupon a combination of additional factors that may impact tractiveefficiency. FIG. 10 illustrates an example database 750 that may beconsulted by controller 60 when selecting a chosen lead for vehicle 10at either a rear speed based upon an operator interface (such asdescribed above with respect to method 200) or a chosen rear speed (suchas described above with respect to method 300). Database 750 comprise anindividual data set (similar to database 150) for each of multipledifferent terrain conditions and/or types and draft/implement factors.In the example illustrated, database 750 comprises data sets 751-1,751-2 . . . 751-N (collectively referred to as data sets 751) fordifferent terrain types/conditions T with different drafts or implementtypes D/I. Database 850 comprises data sets 751-1, 751-2 . . . 751-N forT₁ D/I₁, T₂, D/I₁ . . . T_(N), E/I_(N), respectively. Each of the datasets 751 is similar to database 150 described above except that itsvalues have been determined on the basis of vehicle 10 or a vehiclesimilar to vehicle 10 having a particular draft (range of drafts) and aparticular terrain condition or type. Such values may be empiricallydetermined from prior testing or determined by estimating such valuesfrom previously determined relationships and assumptions.

In such an implementation, controller 60 may receive signals from aterrain sensor, such as a camera or a sensor that directly contacts theground. Controller 60 may identify or determine the type or condition ofthe soil based upon signals from the terrain sensor. In someimplementations, controller 60 may use the current geographic locationof the vehicle and a terrain map to determine the current terraincondition and/or type.

Controller 60 may further determine the current draft of the vehicle 10(based upon signals from a draft sensor, such as a hitch pin connectingthe implement drawbar to the vehicle and having a strain sensor or basedupon signals from various strain sensors attached to the links of thethree-point hitch). In some implementations, the vehicle may be equippedwith an implement sensor to detect or sense the implement and itscurrent operational state. For example, the vehicle may be equipped witha camera and a neural network that utilizes optical recognition toidentify the particular implement. Once a particular implement has beenidentified, the draft associated with the implement and its operationmay be determined. In some implementations, the operator may providecontroller 60 with the implement type or draft value.

Once the current terrain and the current draft or implementidentification/operation has been obtained by controller 60, controller60 may use such information to determine which of the data sets 751should be consulted for selecting the chosen lead. In someimplementations, the operator may directly indicate to controller 60(via an operator interface) which of the data sets 751 should be usedfor selecting the chosen lead.

FIG. 11 illustrates an example database 850 that may be consulted bycontroller 60 when selecting a chosen lead for vehicle 10 at either arear speed based upon an operator interface (such as described abovewith respect to method 200) or a chosen rear speed (such as describedabove with respect to method 300). Database 850 comprise an individualdata set (similar to database 150) for each of multiple differentgeographic regions and/or types and draft/implement factors. In theexample illustrated, database 850 comprises data sets 851-1, 851-2 . . .851-N (collectively referred to as data sets 851) for the differentdrafts or implement types in different geographic regions GR₁ D/I₁,/GR₂, D/I₁ . . . GR_(N), E/I_(N), respectively. Each of the data sets851 is similar to database 150 described above except that its valueshave been determined on the basis of vehicle 10 or a vehicle similar tovehicle 10 having a particular draft (range of drafts) in a particulargeographic region. Such values may be empirically determined from priortesting or determined by estimating such values from previouslydetermined relationships and assumptions.

In such an implementation, controller 60 may receive signals from alocation sensor, such as a GPS antenna having an associated GPSreceiver. Controller 60 may further determine the current draft of thevehicle 10 (based upon signals from a draft sensor, such as a hitch pinconnecting the implement drawbar to the vehicle and having a strainsensor or based upon signals from various strain sensors attached to thelinks of the three-point hitch). In some implementations, the vehiclemay be equipped with an implement sensor to detect or sense theimplement and its current operational state. For example, the vehiclemay be equipped with a camera and a neural network that utilizes opticalrecognition to identify the particular implement. Once a particularimplement has been identified, the draft associated with the implementand its operation may be determined. In some implementations, theoperator may provide controller 60 with the implement type or draftvalue.

Once the current geographic location of the vehicle 10 and the currentdraft or implement identification/operation has been obtained bycontroller 60, controller 60 may use such information to determine whichof the data sets 851 should be consulted for selecting the chosen lead.In some implementations, the operator may directly indicate tocontroller 60 (via an operator interface) which of the data sets 851should be used for selecting the chosen lead.

As described above with respect to FIGS. 3 and 4 , each of the data sets451, 551, 651, 751 and 851 may alternatively be condensed into a table,such as table 154 in FIG. 4 . The condensed table identifies theparticular lead L having the maximum or greatest tractive efficiency forthe particular rear speed RS. Those data sets that are at leastpartially based upon geographic regions may be further condensed intolead maps. For example, with respect to database 550, each of the datasets 551 may be condensed into an optimum tractive efficiency tablesimilar to table 154. The optimum tractive efficiency tables correspondto data sets 551-1, 551-2 . . . 551-N may be condensed into a lead mapsfor different rear speeds.

FIG. 12 illustrates an example map set 900 based upon database 550. Mapset 900 comprises a set of individual lead maps 902-1, 902-2 . . . 902-N(collectively referred to as lead maps 902) for rear speeds RS₁, RS₂ . .. RS_(N), respectively. Each of the example lead maps 902 comprisesgeographic regions 904. Each of the geographic regions 904 has anassociated optimal lead of value L indicating the lead at which thevehicle 10 traveling in the particular geographic region 904 and havingthe particular rear speed RS will achieve the greatest tractiveefficiency TE. As shown by FIG. 12 , the regions 904 of different maps902 may have different sizes, shapes and numbers depending upon wheretractive efficiencies change such that the recommended lead values alsochange. As should be appreciated, the size, shape and number ofdifferent regions 904 may vary in multiple fashions.

When vehicle 10 is operating in a map-based mode, controller 60 mayreceive signals from rear speed sensor 50 indicating the rear speed ofrear traction members 24. Based upon such signals, controller 60 mayselect which of the particular maps 902 to consult. Upon determining thecurrent location of vehicle 10, such as from a GPS antenna or by othermethods, controller 60 may determine in which of the regions 904 in theparticular map 902 that vehicle 10 currently resides. Upon determiningwhich region of the particular map vehicle 10 resides, controller 60 maydetermine the recommended lead of value L from of the map. At such time,controller 60 may either output the recommended lead to an operator ofvehicle 10 and/or may automatically output control signals causing frontdrive system 32 to drive front wheel 26 at the recommended lead L.

FIG. 13 illustrates an example map set 1000 based upon database 850. Mapset 1000 comprises a set of individual lead maps 1002-1, 1002-2 . . .1002-N (collectively referred to as lead maps 1002) for rear speeds RS₁,RS₂ . . . RS_(N), and draft/implements D/I₁, D/I₂, . . . D/I_(N),respectively. Each of the example lead maps 1002 comprises geographicregions 1004. Each of the geographic regions 1004 has an associatedoptimal lead of value L indicating the lead at which the vehicle 10traveling in the particular geographic region 1004 with the particularrear speed RS and with the particular draft D or implement I (operationand/or type) will achieve the greatest tractive efficiency TE. As shownby FIG. 13 , the regions 1004 of different maps 1002 may have differentsizes, shapes and numbers depending upon where tractive efficiencieschange such that the recommended lead values also change. As should beappreciated, the size, shape and number of different regions 1004 mayvary in multiple fashions.

When vehicle 10 is operating in a map-based mode, controller 60 mayreceive signals from rear speed sensor 50 indicating the rear speed ofrear traction members 24. Controller 60 may further receive signals froma draft sensor or from an implement sensor indicating the current draftforce (pulling force) or implement being pulled by the vehicle. Basedupon such signals, controller 60 may select which of the particular maps1002 to consult. Upon determining the current location of vehicle 10,such as from a GPS antenna or by other methods, controller 60 maydetermine in which of the regions 1004 in the particular map 1002 thatvehicle 10 currently resides. Upon determining which region of theparticular map vehicle 10 resides in, controller 60 may determine therecommended lead value L from the map. At such time, controller 60 mayeither output the recommended lead to an operator of vehicle 10 and/ormay automatically output control signals causing front drive system 32to drive front wheel 26 at the recommended lead L.

FIGS. 14-17 illustrate portions of an example vehicle 1110 whichincludes an example lead control system 1120. FIGS. 14-17 illustrate anexample of how the vehicle described above with respect to FIG. 1 may beembodied as a tractor and may be provided with various operatorselectable modes and additional optional features for not onlycontrolling the lead of the vehicle but also acquiring tractiveefficiency data for use by other vehicles in controlling their leads.Vehicle 1110 is in the form of an agricultural tractor and comprisesframe 1224, operator cab 1225, propulsion system 1228, rear wheels 1124(which serve as rear ground traction members) and steered front wheels1126 (which serve as front ground traction members), clevis hitch 1227(shown in FIG. 15 ), hitch pin 1229 (shown in FIG. 15 ) and three-pointhitch 1229 (a portion of which is shown in FIG. 14 ).

Frame 1224 comprises a structure which supports the remaining componentsof vehicle 1110. Frame 1224 supports operator cab 1225. Operator cab1225 comprises that portion of vehicle 1110 in which an operator ofvehicle 1110 resides during use of vehicle 1110. In the exampleillustrated, operator cab 1225 comprises seat 1216, operator interface1217, and roof 1218. Seat 1216 is beneath roof 1218.

Operator interface 1217 is positioned proximate to seat 1216 andincludes various controls by which an operator may exert control over avehicle 1110 and receive information regarding the operation of vehicle1110 and any attached implements. Operator interface 1217 (schematicallyillustrated) may comprise multiple input devices in the form of footpedal, a lever, a touchscreen, a monitor and mouse, keyboard, a touchpad, a joystick, a stylus pen, a toggle switch, slide bar, a microphonewith speech recognition or the like. For example, a foot pedal or levermay be utilized buying operator to select a ground speed for vehicle1110. Information may be provided to the operator on a display screen,series of LED lights or the like. In implementations where vehicle 1110is configured to be remotely controlled, operator interface 1217 may beremote from the remainder of vehicle 1110, wherein signals from operatorinterface 1217 communicate with vehicle 1110 in a wireless fashion.

Propulsion system 1228 serves to propel vehicle 1110 in forward andreverse directions. As shown by FIG. 16 , propulsion system 1228comprises battery 1230, electric motor 1232, torque splitter 1234,transmission 1235, transaxle 1238, hydraulic pump 1240, hydraulic motor1242 and front wheel transmission 1244. Battery 1230 comprises one ormore battery modules which store electrical energy. Battery 1230 issupported within an internal battery receiving cavity provided by frame1224. Battery 1230 powers the electric motor 1232.

Electrical motor 1232 (schematically illustrated) outputs torque whichis transmitted by a gearing to torque splitter 1234. Torque splitter1234 transmits torque to transmission 1235 and to hydraulic pump 1240.Transmission 1235 provides a plurality of forward and reverse gearsproviding different rotational speeds and torques to the rear wheels1124.

Transaxle 1236 extends from transmission 1235 and transmits torque tofront wheel transmission 1244 for rotatably driving the front steeredwheels 1126. Hydraulic pump 1240 is driven by the torque provided byelectric motor 1232. Hydraulic pump 1240 supplies pressurized hydraulicfluid to drive hydraulic motor 1242. Hydraulic motor 1242 suppliestorque to front wheel transmission 1244. This additional torquefacilitates the rotatable driving of front wheels 1126 at speeds thatproportionally differ than the rotation speeds at which rear wheels 1124are being driven by transmission 1235.

Front wheel transmission 1244 delivers torque from one or both oftransaxle 1236 and hydraulic motor 1242 to front wheels 1126. FIG. 17illustrates portions of one example propulsion system 1228 includinghydraulic pump 1240, hydraulic motor 1242 and planetary gear assembly1246. Hydraulic pump 1240 powers hydraulic motor 1242. In the exampleillustrated, hydraulic pump 1240 comprises a continuous input variabledisplacement hydraulic piston pump. Hydraulic motor 1242 comprises amodulation hydraulic motor.

Planetary gear assembly 1246 combines torque from transaxle 1238 andfrom hydraulic motor 1242 and outputs the combined torque to frontwheels 1126 (shown In FIGS. 14 and 16 ) which are connected to frontwheel flanges 1248. Planetary gear assembly 1246 comprises a sun gear1250, ring gear 1252 and planet carrier 1254 supporting planet gears1256 which intermesh with sun gear 1250 and ring gear 1252.

Sun gear 1250 serves as a first input for planetary gear assembly 1246.Sun gear 1250 is connected to and receives torque from output shaft ofhydraulic motor 1242. Ring gear 1252 serves as a second input forplanetary gear assembly 1246. Ring gear 1252 is connected to transaxle1238 by a gear set 1260. In other implementations, ring gear 1252 may beconnected to transaxle 1238 by other transmission mechanisms such asbelt and pulley arrangement or a chain sprocket arrangement. Planetcarrier 1254 is connected to gear set 1262 and serves as an output forplanetary gear assembly 1246.

Gear set 1262 comprises a pair of bevel gears connected to differential1264. Differential 1264 outputs torque to gear sets 1266-L and 1266-Rwhich further transmit torque to gear sets 1268-L and 1268-R which areconnected to left and right wheel flanges 1248.

FIGS. 16 and 17 illustrate one example of propulsion system 1228. Inother implementations, propulsion system 1228 may have other forms orconfigurations. For example, in other implementations, propulsion system1228 may comprise other combinations of electric motors, hydraulic pumpsand hydraulic in some implementations, vehicle propulsion system 1228may omit hydraulic systems. In some implementations, propulsion system1228 may omit electric motors, such as where vehicle propulsion system1228 relies upon an internal combustion engine for supplying torquedirectly to the transmissions or using hydraulic pumps and motors.

Rear wheels 1124 extend at a rear portion of frame 1224 of vehicle 1110and are not steerable while front wheels 1126 extend at a front portionof the frame 1224 and are steerable. Front wheels 1126 are rotatablysupported by frame 1224 and are configured to be rotatably driven atdifferent speeds or revolutions for minute relative to the speeds atwhich rear wheels 1124 are driven.

Battery 1230, electric motor 1232, and transmission 1235 serve as a reardrive system for driving rear wheels 1124. Battery 1230, electric motor1232, hydraulic pump 1240, hydraulic motor 1242 and forward transmission1244, including planetary gear assembly 1246, serve as a continuousvariable speed front drive system. Hydraulic motor 1242 is configured tobe modulated so as to vary the rotational speed at which front wheels1126 are driven relative to the speed at which rear wheels 1124 aredriven. Through the modulation of hydraulic motor 1242, the lead offront wheels 1126 may be adjusted and controlled.

Clevis hitch 1227 projects from the rear of vehicle 1110 and isconfigured to receive an implement drawbar 1231. Clevis hitch 1227includes a pair of aligned apertures, which when aligned with anaperture of drawbar 1231, receive hitch pin 1229 to connect an implement1233 (schematically illustrated) to vehicle 1110 that is to be pulled ortowed.

Three-point hitch 1229 projects from the rear of vehicle 1110 includesan upper link and a pair of lower links for being connected to animplement, such as implement 1233, that is to be pulled or towed.

Lead control system 1120 is similar to lead control system 20 describedabove in that lead control system 1120 selects a chosen lead for thefront wheels 1126 relative to the rear speed of rear wheels 1124 basedupon an evaluation of different tractive efficiencies for differentleads for the particular rear speed. Lead control system 1120 furtheroutputs control signals to a continuously variable speed front drivesystem by outputting control signals to hydraulic motor 1242 to modulatehydraulic motor 1242 so as to drive the front ground traction members orwheels 1126 with the chosen lead. The control signals may be outputautomatically upon selecting the chosen lead or may be output aftersystem 1120 has recommended the chosen lead to an operator and after theoperator has confirmed or authorized the switch to the chosen lead.

Lead control system 1120 comprises rear speed sensor 1150, front speedsensor 1154, geographic location sensor 1172, terrain maps 1174, terrainsensor 1176, implement sensor 1178, implement database 1180, draftsensor 1182, radar-Doppler sensor 1184, lead databases 1186, lead maps1188 and controller 1160. Rear speed sensor 1150 comprise a sensorconfigured to output signals indicating a current rotational speed atwhich rear ground traction members in the form of wheels 1124 are beingdriven. Such signals may directly indicate the sensed rotationalvelocity of rear ground traction members 24 or may indirectly indicatethe sensed rotational velocity of the rear wheels 1124, wherein therotational velocity may be derived from such signals by controller 1160.In one example implementation, rear speed sensor 1150 may comprise whatis commercially available as a “wheel speed sensor” or “vehicle speedsensor”. Such a wheel speed sensors may comprise a toothed ring andpickup sized to read the speed of vehicle wheel rotation. Such sensorsmay utilize optics, magnetics or other mechanisms.

Front speed sensor 1154 is similar to rear speed sensor 1150 except thatfront speed sensor 1154 comprises a sensor configured to output signalsindicating a current rotational speed at which the front ground tractionmembers, in the form of front wheels 1126, are being driven. Suchsignals may directly indicate the sensed rotational velocity of rearground traction members 1126 or may be indirectly indicate the sensedrotational velocity of the rear ground traction members 1126, whereinthe rotational velocity may be derived from such signals by controller60. In one example implementation, front speed sensor 1154 may comprisewhat is commercially available as a “wheel speed sensor” or “vehiclespeed sensor”. Such a wheel speed sensors may comprise a toothed ringand pickup sized to read the speed of vehicle wheel rotation. Suchsensors may utilize optics, magnetics or other mechanisms.

Geographic location sensor 1172 comprises one or more sensors configuredto output signals to controller 1160 to facilitate the identification ofthe geographic location of vehicle 1110 by controller 1160. Signals fromgeographic location sensor 1172 may be further used to identify a groundspeed of vehicle 1110. In the example illustrated, geographic locationsensor 1172 comprises a global positioning system (GPS) antenna. The GPSantenna comprises an antenna situated upon roof 318 and provided as partof a larger global positioning satellite system, global navigationsystem (GNS) or other satellite-based radio navigation system. Theantenna may be associated with a GPS receiver.

Terrain maps 1174 comprise maps indicating different terrain conditionsand/or types for different geographical regions. Terrain maps may bestored locally on vehicle 1110 or may be remote, being accessed from aserver by controller 1160 in a wireless fashion. Based upon signals fromgeographic location sensor 1172 and terrain maps 1174, controller 1160may determine the type or conditions of the terrain 1190 currentlyunderlying or about to underlie vehicle 1110.

Terrain sensor 1176 comprise a sensor configured to sense the soil orunderlying terrain 1190. In some implementations, terrain sensor 1176may comprise a camera carried by vehicle 1110, such as near an undersideof vehicle 1110. Images captured by the so sensor 1176 may be utilizedto determine the type and such or condition of the underlying terrain1190. As described above, in some circumstances, the type and such orcondition of the underlying terrain may have an impact upon tractiveefficiencies.

Implement sensor 1178 comprise a sensor configured to sense anyimplement currently attached or being pulled by vehicle 1110. In someimplementations, implement sensor 1170 may comprise a camera mountedproximate a rear of vehicle 1110 and having a field-of-view thatincludes an attached implement 1233. In such an implementation, a neuralnetwork, trained to identify implements, may be utilized to analyzeimages of implement 1233 to identify the particular implement 1233and/or its characteristics. Implement database 1180 comprise a databaseidentifying draft values associated with different implements. Asdiscussed above, based upon an identification of the implement beingpulled, controller 1160 may determine a draft force being provided byvehicle 1110.

Draft sensor 1182 comprise a sensor to directly sense the draft ofvehicle 1110. Draft sensor 1182 may be operative coupled betweenimplement 1233 and vehicle 1110. For example, as shown in FIG. 15 , insome implementations, the hitch pin 1229 may be provided with a strainsensor 1192 which serves as a draft sensor to sense a pulling forceprovided by vehicle 1110. In some implementations, the links of thethree-point hitch 1229 may be provided with similar strain sensors forsensing the force of vehicle 1110 during pulling of implement 1233.

Radar-Doppler sensor 1184 comprise a sensor carried by vehicle 1110 andconfigured to output signals indicating a ground speed for vehicle 1110.In such an implementation, sensor 1184 fires a radar beam towards theground or other structure and measures a Doppler shift of the returningbeam for the calculation of a speed of the vehicle. As will be describedhereafter, the detected ground speed may be used by controller 1160 tocarry out tractive efficiency determinations and to populate leaddatabases 1186 and lead maps 1188 with tractive efficiency data.

Lead databases 1186 comprise databases that provide either differenttractive efficiencies for different leads under certain conditions orthose leads that have the largest tractive efficiency under selectedconditions. Lead databases 1186 may comprise databases 450, 550, 650,750 and 850 described above. Controller 1160 may consult such databasesto select a chosen lead for the front wheels 1126 of vehicle 1110.

Lead maps 1188 identify recommended leads for different geographiclocations based upon certain conditions such as the implement beingtowed, the sensed draft of the vehicle, and/or terrain conditions and/ortypes. Lead maps 1188 may comprise lead maps such as lead maps 900 and1000 described above. Controller 1160 may consult lead maps, based uponthe current sensor determining conditions to select a chosen lead.

Controller 1160 comprises memory 1162 and processor 1164. Memory 1162comprises a non-transitory computer-readable medium containinginstructions for directing processor 1164. Processor 1164 comprises aprocessing unit configured to follow such instruction contained inmemory 1162. Instructions contained in memory 1162 may direct processorloan 64 to carry out method 100 and its various forms, wherein thecontroller selects a chosen lead and outputs control signals providingthe vehicle with the chosen lead. Controller 1160 may operate in one ofvarious operator selected modes based upon input received throughoperator input 1217.

In the example illustrated, lead control system 1120 is operable in afirst mode in which method 200, described above, is performed, and asecond mode in which method 300, described above, is performed. In theexample illustrated, lead control system 1120 may be operable in anoperator selected mode during which controller 1160 selects the chosenlead based upon the current or anticipated rear speed of rear wheels1124 and database 150 or table 154 pursuant to method 200 or 300 asdescribed above. In such a mode, the database 150 and the table 154 havetractive efficiencies that have been previously determined based upon adefault terrain soil or condition (median or average values) and adefault draft values (median, average or other selected values).

Lead control system 1120 may be operable in an operator selected modeduring which controller 1116 determines the current or forthcomingterrain conditions and/or type based upon signals from terrain sensor1176 and/or based upon the geographic location of vehicle 1110. Theterrain type and/or condition may be determined from location of vehicle1110 (determined based upon signals from identification sensor 1172) andthe terrain maps 1174. Controller 1160 utilizes the identified terraintype and/or condition to determine which of data sets 451 in database450, found in lead databases 1186, to use to select the chosen leadbased upon the current or anticipated rear speed RS. In such a mode,database 450 may have tractive efficiencies that have been previouslydetermined based upon default draft values (median, average values orother selected values).

Lead control system 1120 may be operable in an operator selected modeduring which controller 1160 determines a geographic location of vehicle1110 based upon signals from location identification sensor 1172.Controller 1160 utilizes the identified geographic location of vehicle1110 to determine which of the data sets 551 of database 550, found inlead databases 1186, to use to select the chosen lead based upon thecurrent or anticipated rear speed RS. In such a mode, database 550 mayhave tractive efficiencies that have been previously determined basedupon default draft values (median, average values or other selectedvalues).

Lead control system 1120 may be operable in an operator selected modeduring which controller 1160 determines the current draft of vehicle1110 or the current implement being pulled by vehicle 1110, whereincontroller 1160 may determine a draft value based upon the implementbeing pulled. Controller 1160 may determine the current draft valuebased upon signals from draft sensor 1182, such as with a strain sensor1192 associated with a hitch pin 1229 or strain sensors associated withlinks of a three-point hitch. In some implementations, controller 1160may determine the implement and/or its state based upon signals fromimplement sensor 1178 and implement database 1180.

Controller 1160 utilizes the identified implement and/or state, or thedetermined draft to determine which of the data set 651 of database 650,found in lead databases 1186, to use to select the chosen lead basedupon the current or anticipated rear speed RS. In such a mode, database650 may have tractive efficiencies that have been previously determinedbased upon a default terrain soil or condition (median or averagevalues).

Lead control system 1120 may be operable in an operator selected modeduring which controller 1160 determines both the terrain type/conditionand the current draft/implement. Such determinations may be made asdescribed above. Controller 1160 may utilize both determinations todetermine which of the data sets 751 of database 750, found in leaddatabases 1186, to use to select the chosen lead database based upon thecurrent or anticipated rear speed RS.

Lead control system 1120 may be operable in an operator selected modeduring which controller 1160 determines both geographic location of the1110 and the current draft/implement. Such determinations may be made asdescribed above. Controller 1160 may utilize both determinations todetermine which of the data sets 851 of database 850, found in leaddatabases 1186, to use to select the chosen lead based upon the currentor anticipated rear speed RS.

Lead control system 1120 may be operable in an operator selected modeduring which controller 1160 selects one of the lead maps 902, found inlead maps 1188, based upon the current anticipated rear speed based uponthe current or anticipated rear speed RS. Control 1160 may furtherdetermine the geographical location of vehicle 1110 (in a manner asdescribed above) to determine in which region of the particular map 902vehicle 1110 currently resides. Based upon the current region 904 inwhich vehicle 1100 currently resides in the particular map 902,controller 1160 may select the chosen lead.

Lead control system 1120 may be operable in an operator selected modeduring which controller 1160 selects one of the lead maps 1002, found inlead maps 1188, based upon a combination of both the current oranticipated rear speed of vehicle 1110 and the determined draft orimplement type/state. The draft or implement type and such or state maybe determined in a manner as described above. Lead control system 1120may further determine the geographical location of vehicle 1110 (in amanner described above) to determine the region of the particular map1002 in which vehicle 1110 currently resides. Based upon the currentregion 1004 in which vehicle 1110 currently resides in the particularmap 1002, controller 1160 may select the chosen lead.

Lead control system 1120 may be further operable in a user selected modeduring which controller 1160 determines different tractive efficienciesassociated with different vehicle leads when operating under certainconditions. The determined tractive efficiencies may be used to populatelead database 1186 and lead maps 1188, wherein the traction areempirically determined by vehicle 1110. In such a mode, controller 1160determines and records, in real-time, different tractive efficienciesfor different leads for each of multiple different rear speeds of thevehicle 1110.

Tractive efficiency (also referred to as traction efficiency), may bedetermined based upon the formula: (Ground speed*draft)/(torque*wheelspeed). Controller 1160 may obtain values for the ground speed basedupon signals from either location identification sensor 1172 or theradar-Doppler sensor 1184. Controller 1160 may obtain values for thedraft based upon signals from draft sensor 1182 or the implement sensor1170 and implement database 1180.

Controller 1160 may obtain values for the torque based upon signalsreceived from current sensor 1194 (shown in FIG. 16 ) and/or strainsensors (StS) 1196 (shown in FIG. 16 ). Current sensor 1194 senses thecurrent being drawn by electric motor 1232 to provide to rear wheels1124 and front wheels 1126. Strain sensors 1196 sense the torque beingapplied to rear wheels 1124 and front wheels 1126.

Controller 1160 may obtain wheel speed values from rear speed sensor1150 and/or front speed sensor 1154.

In some implementations, the controller 1160 may adjust the rear speedof the vehicle 1110 by outputting control signals to electric motor 1232and transmission 1235, wherein for each individual rear speed of thevehicle 1110, the controller may further adjust the speed of the frontground traction members or wheels, by providing control signals tomodulate the hydraulic motor 1242 to provide different leads. For eachof the leads at each individual rear speed, controller 1160 may utilizeground speed, draft, torque and wheel speed data (discussed above) todetermine the resulting tractive efficiency. In such an implementation,the controller 1160 may generate a table or database identifyingdifferent tractive efficiencies for different leads for each of thedifferent rear speeds.

In some implementations, the controller 1160 may record the differenttractive efficiencies for the different leads for each of the differentrear speeds with different draft values, such as when the vehicle ispulling different implements or providing different drafts, producing adatabase that further takes into account the particular draft beingpulled by the vehicle. In some implementations, the controller 1160 mayrecord the different tractive efficiencies for the different leads foreach of the different rear speeds when the vehicle traveling atdifferent geographic locations or is traveling across different terrainshaving different soil conditions and/or types, producing database thatfurther takes into account the particular terrain or condition of theunderlying terrain or soil. Such databases may be provided as part oflead databases 1186 and may be subsequently utilized by other vehiclesof the same type or may be used as a basis for the selection of chosenleads for other or different types of vehicles.

In operator selected modes, controller 1160 may determine tractiveefficiency based upon a measurement of fuel or battery powerconsumption. Controller 1160 may receive control signals indicating therate at which charge is drained from battery 1230. In such animplementation, controller 1160 may determine tractive efficiency byevaluating how much fuel or battery power was consumed by the vehicle1110 to pull implement 1233, providing a given load or draft, at aparticular ground speed (as determined based upon signals from sensor1170 to or 1184). This evaluation may be done for each evaluated wheelspeed and each of the leads being evaluated for each wheel speeds. Theresults may be recorded to form a database of leads. As describedhereafter, the results may be further conditioned or based on variationsin the implement being towed (variations in the draft), variations inthe geographic regions in which vehicle 1110 is operating, and/orvariations with respect to the underlying terrain.

Each of the above example implementations has been described in thecontext of measuring tractive efficiencies and/or automaticallyselecting and executing a vehicle lead based upon such tractiveefficiencies. In other implementations, such implementations mayalternatively or additionally provide an operator with the ability tothe vehicle measures traction and/or automatically selects and executesa vehicle lead based upon such tractions or traction levels. In otherwords, traction, rather than traction efficiency, is the targetvariable. Lead will be selected to optimize the traction, rather thanthe traction efficiency, for the vehicle.

Maximum traction can be determined, similarly, but based on the maximumreadings of the draft sensor until the draft stops increasing and levelsoff or goes down. Maximum traction, or coefficient of traction, can beuseful in momentary situations for the vehicle to deal with patches ofhard soil. In such example implementations, lead control system 1120 maybe operable in a operator selectable mode in which system 1120 consultsdatabases or tables similar to those described above, but wherein thetargeted variable is traction rather than traction efficiency. System1120 may automatically output control signals causing the vehicle toprovide a particular lead at a particular rear speed to achieve anoptimum or maximum traction for the vehicle. As above, the database ortables may be based upon a single variable, such as rear speed (combinedwith default or standard variables such as draft, implement type orstate, geographic region, tire pressure or terrain) or may be based uponcombinations of multiple variables comprising one or more of rear speed,draft, implement type or state, geographic region, tire pressure andterrain.

FIG. 18 is a diagram illustrating an example database 1350 comprisingdata sets 1351-1, 1351-2 . . . 1351-N (collectively referred to as datasets 1351). Each of data sets 1351 comprises values at a particulargeographic region GR and with a particular draft or implement state/typeD/I. Each of data sets 1351 comprises a set of tables 1451-1, 1451-2 . .. 1451-N (collectively referred to as tables 1451), wherein each oftables 1451 identify an associated traction T (rather than tractionefficiency TE) for a particular vehicle lead L at a particular rearspeed RS. Such values may be empirically determined and stored usingdefault or standard variables for other conditions such as tirepressure, terrain type or the like. In a fashion similar to thatdescribed above with respect to selecting a lead based upon tractionefficiency, system 1120 may likewise be operable in an operatorselectable mode in which system 1120 alternatively identifies andimplements a particular vehicle lead based upon the current geographicregion, and draft/implement type, state to enhance or optimize tractionfor the vehicle.

Although the present disclosure has been described with reference toexample implementations, workers skilled in the art will recognize thatchanges may be made in form and detail without departing from the scopeof the claimed subject matter. For example, although different exampleimplementations may have been described as including features providingbenefits, it is contemplated that the described features may beinterchanged with one another or alternatively be combined with oneanother in the described example implementations or in other alternativeimplementations. Because the technology of the present disclosure isrelatively complex, not all changes in the technology are foreseeable.The present disclosure described with reference to the exampleimplementations and set forth in the following claims is manifestlyintended to be as broad as possible. For example, unless specificallyotherwise noted, the claims reciting a single particular element alsoencompass a plurality of such particular elements. The terms “first”,“second”, “third” and so on in the claims merely distinguish differentelements and, unless otherwise stated, are not to be specificallyassociated with a particular order or particular numbering of elementsin the disclosure.

What is claimed is:
 1. A vehicle comprising: rear ground tractionmembers; front ground traction members; a rear drive system to drive therear ground traction members; a continuously variable speed front drivesystem to drive the front ground traction members; a rear speed sensorto output rear speeds of the rear ground traction members; a front speedsensor to output front speeds of the front ground traction members; anda controller to: select a chosen lead for a rear speed of the rearground traction members based on evaluations of different tractiveefficiencies for different leads for the rear speed; and output controlsignals to the continuously variable speed front drive system to drivethe front ground traction members at the chosen lead.
 2. The vehicle ofclaim 1 further comprising an operator interface to receive a groundspeed input from an operator, wherein the rear speed is based upon theground speed input.
 3. The vehicle of claim 1, wherein the controller isconfigured to select the rear speed based upon different tractiveefficiencies for different leads for each of multiple different rearspeeds.
 4. The vehicle of claim 1 further comprising a databasecomprising the evaluations of different tractive efficiencies fordifferent leads for each of multiple different rear speeds.
 5. Thevehicle of claim 1, wherein the controller is configured to select thechosen lead additionally based upon a geographic location of thevehicle.
 6. The vehicle of claim 5 further comprising a lead mapidentifying different recommended leads for the rear speed at differentgeographic locations, wherein the controller is configured to consultthe lead map based upon the geographic location of the vehicle.
 7. Thevehicle of claim 1, wherein the controller is configured to select thechosen lead additionally based upon a current condition and/or type ofterrain underlying the vehicle.
 8. The vehicle of claim 7 furthercomprising a terrain map identifying different conditions and/or typesof terrain at different geographic locations, wherein the controller isconfigured to consult the terrain map based upon a geographic locationof the vehicle.
 9. The vehicle of claim 1, wherein the controller is tooutput a recommendation for the chosen lead to an operator, wherein thecontrol signals are output in response to further operator interface.10. The vehicle of claim 1, wherein the controller is configured toautomatically output the control signals in response to the selection ofthe chosen lead.
 11. The vehicle of claim 1, wherein the controller isconfigured to select the chosen lead additionally based upon a currentdraft of the vehicle.
 12. The vehicle of claim 11 further comprising adraft sensor to output signals to the controller indicating the currentdraft of the vehicle.
 13. The vehicle of claim 11 further comprising animplement identification sensor to output implement identificationsignals to the controller, wherein the controller is configured toidentify an implement currently attached to the vehicle and to determinethe current draft of the vehicle based upon the implement currentlyattached to the vehicle.
 14. The vehicle of claim 1, wherein thecontroller is configured to select the chosen lead based upon animplement attached to the vehicle.
 15. The vehicle of claim 1, whereinthe controller is configured to determine and record the evaluations ofdifferent tractive efficiencies for different leads for each of multipledifferent rear speeds.
 16. The vehicle of claim 15 further comprising: aground speed sensor to output signals indicating a ground speed of thevehicle; and a torque sensor to output signals indicating torque appliedto the rear ground traction members and the front ground tractionmembers, wherein the controller is configured to determine theevaluations of different tractive efficiencies for different leads foreach of multiple different rear speeds based upon different groundspeeds of the vehicle, different torques applied to the rear groundtraction members and the front ground traction members, different draftvalues for each of the different leads for each of the multipledifferent rear speeds.
 17. The vehicle of claim 15 further comprising adraft sensor for outputting signals indicating the different draftvalues.
 18. The vehicle of claim 15 further comprising an implementsensor for outputting signals indicating an identification of animplement attached to the vehicle and/or a state of the implement, theimplement and/or a state of the implement corresponding to a particulardraft value.
 19. The vehicle of claim 1, wherein the controller isconfigured to determine and record the evaluations of different tractiveefficiencies for different leads for each of multiple different rearspeeds.
 20. The vehicle of claim 1, wherein the continuously variablespeed front drive system comprises: an electric motor; a hydraulic pumpdriven by the electric motor; and a hydraulic motor driven by thehydraulic pump and operably coupled to the front ground traction membersby a planetary gear assembly, the planetary gear assembly comprising: asun gear coupled to and driven by the hydraulic motor; a ring gearcoupled to and driven by the electric motor; and a planet carriercarrying planet gears intermeshing between the ring gear and the sungear, the planet carrier having an output shaft operably coupled to thefront ground traction members to drive the front ground tractionmembers.